The home secretary might try to brazen out Polly Taylor's resignation from the Advisory Council on the Misuse of Drugs (ACMD). If so, the government's claim that it values independent scientific advice will take another knock. Waiting to impose a ban on mephedrone until the ACMD reports is not the same as basing a decision on scientific advice. The Home Office had already decided to ban mephedrone. The ACMD's deliberations were mere window dressing. So it is worth considering how the process of classifying a drug generally operates.

Under the 1971 Misuse of Drugs Act the home secretary is obliged to consult the ACMD about any proposed changes to a drug's classification.

Following discussion with the Home Office, an ACMD working group will draw up a draft report, normally over a period of four or five meetings. It will then go to the full ACMD for agreement, after which the ACMD will write to the home secretary with its recommendation. This is painstaking, detailed and time-consuming work.

After giving the report due consideration, the home secretary makes his or her response. There then comes the formal consultation, lasting 12 weeks, and a regulatory impact assessment. Both houses of parliament then need to approve any change, as does the privy council. Following this the new classification becomes law.

In normal times the whole process takes a year and a half, sometimes longer. The deliberations that led to cannabis being reclassified from class B to class C in January 2004 came on the back of an ACMD-led review that lasted close to two and half years.

But these are not normal times. We are in the middle of a mephedrone scare in the runup to a general election. The result of this toxic combination is the current farrago.

Since the mass resignations in the wake of David Nutt's dismissal, the ACMD has been unable to function. New members, originally due for interview in April, are now hurriedly being put into place.

A report has been rushed through a depleted technical committee. Most of the ACMD members will not even get to see it until today's meeting, at which they will be expected to make a potentially far-reaching recommendation on classification.

The interim chair, Les Iversen, has been put in an impossible position. I can not imagine that any of the current ACMD members can be feeling too good right now. We are facing a rush classification of a drug, the harms of which are still little understood. Indeed, some are openly questioning the principle of a science-based drugs classification system. The whole thing is a mess.

Yet even at this late stage there is a chance to do things differently. The European Monitoring Centre on Drugs and Drug Addiction, an EU body that provides factual analysis for member countries, is conducting its own study of mephedrone and is likely to report in July. This should give a far more rounded view of the evidence than the ACMD alone can provide.

It is also about time that there was a serious debate about the alternatives to outright criminalisation. As David Nutt argued last week in the Evening Standard, legal, though regulated, supply of drugs like mephedrone, ecstasy and cannabis might be a better way of reducing the undoubted harms of drug taking than an approach that criminalises users.

Criminalisation, at the end of the day, is a pretty blunt and ineffective mechanism for controlling certain behaviours deemed criminal. It is a thoroughly inappropriate means for seeking to protect individuals from the harms drugs cause, or ensuring they have the right kind of information to make informed choices.